There have been a variety of known display apparatus capable of displaying images for a plurality of viewpoints, for example, displaying images having parallax therebetween for stereoscopic vision. An example of a display apparatus of this type under development toward commercialization is a combination of a lenticular lens or any other similar lens array and a display unit that displays two-dimensional images.
FIGS. 16A and 16B are conceptual diagrams showing the operation of a display apparatus having a lens array formed of lens columns disposed between a display unit and an image viewer.
A group of light rays emitted from a group of pixels labeled with reference characters R1, R3, R5, R7, and R9 reach a viewpoint 2, as shown in FIG. 16A. Similarly, a group of light rays emitted from a group of pixels labeled with reference characters L2, L4, L6, L8, and L10 reach a viewpoint 1, as shown in FIG. 16B. In positions from the display unit set apart by a predetermined distance, an image at the viewpoint 1 and an image at the viewpoint 2 are thus viewed independently.
When the left and right eyes of the image viewer are located at the viewpoints 1 and 2 respectively, and the group of pixels labeled with reference characters L2, L4, L6, L8, and L10 and the group of pixels labeled with reference characters R1, R3, R5, R7, and R9 display an image for the left eye and an image for the right eye respectively, the image viewer recognizes the images stereoscopically.
On the other hand, it is preferable for such a display apparatus capable of displaying images for a plurality of viewpoints (displaying stereoscopic images, for example) to be also capable of readily displaying regular images (two-dimensional images) as necessary. In other words, a display apparatus of this type is desirably configured to be capable of switching a display mode between a mode for displaying stereoscopic images or other similar images and a mode for displaying regular images. When the lens columns of the lens array have variable refracting power, the mode for displaying stereoscopic images or other similar images can be switched to the mode for displaying regular images and vice versa.
For example, JP-A-7-72445 proposes a variable lens array capable of changing the refracting power of each lens column, as shown in FIG. 2 in JP-A-7-72445. The variable lens array described in JP-A-7-72445 has a structure in which a liquid crystal layer is disposed between a pair of transparent substrates each having a transparent electrode. In the variable lens array having the structure described above, each lens column is formed of a gradient index lens made of a liquid crystal material (hereinafter simply referred to as GRIN lens in some cases), and the refracting power of the lens column can be changed by changing the voltage between the pair of substrates.